Standard video compression algorithms such as the MPEG2 standard of the International telecommunication Union's Moving Pictures Experts Group and the H.264 of the Video Coding Experts Group compress video sequences known as Groups of Pictures (GOPs). Each GOP has a respective beginning and/or ending boundary and contains video content that lasts a fraction of a second to as long as several seconds. While video is one example of streaming media in the context of the present invention, it is not the only type of streaming media. Broadly, streaming media includes other forms of media such as audio media and non-video forms of visual media.
Channel change latency is important to the satisfactory television viewing experience and other types of streaming media experiences. Switching to a highly compressed digital video stream can take a second or more before the image begins to be displayed. For example, a video decoder cannot begin decoding a video stream until a GOP boundary is recognized. Accordingly, if upon a channel change a decoder begins receiving a new video stream while a GOP transmission of a previous video stream is in progress, the video decoder must wait for the next GOP boundary of that video stream before beginning decoding GOPs of the new stream.
This need to wait for the next GOP boundary increases channel change latency by approximately the “wait time” for the next GOP boundary to present itself. One conventional approach for decreasing the wait time is to have short GOPs so that the wait time is relatively brief. However, compressing video with short GOPs is less efficient than for long GOPs. So, there is a trade off between compression efficiency and channel change latency. Another conventional approach for decreasing the wait time is to begin streaming at the beginning of a GOP upon receipt of a channel change request. However, because channel change requests between different viewers are not synchronous, each media stream must be unicast to a particular decoder, until another mechanism allows alignment and subsequent joining of that unicast media stream to a corresponding multicast media stream.
Conventional approaches for media stream channel changes also adversely impact network resource utilization. In the case where a unicast media stream associated with a channel change originates from a distant source and must traverse core and aggregation networks, then an enormous volume of traffic must be transported. Furthermore, because channel change requests tend to be concentrated on the hour and half hour (i.e., when programs begin), traffic volume associated with channel changes is also extremely variable. Lastly, depending on the channel change concurrency and the duration of unicasting phase associated with channel change requests, network resources that have to be available for rapid channel change may exceed the network resources that are required for the delivery of voice, video, and data services.
Therefore, a media channel changing mechanism that at least partially overcomes drawbacks associated with conventional approaches for changing media channels is useful and advantageous.